Hydraulic brake systems are common in motor vehicles. Brake systems are increasingly being used in which it is possible to carry out braking actions which are executed independently of a braking request by the driver using assistance systems with the aid of electrical or electronic means. Such braking actions which are controlled by electronic control devices are required for example for realizing adaptive cruise control functions or (emergency) brake assist functions.
Brake-by-wire brake systems are further known, which, in the event of a normal brake actuation by the driver, also detect the brake actuation electronically and implement the corresponding braking action in an electronically controlled manner without the driver thereby gaining direct mechanical or hydraulic access to the wheel brakes. In such systems, the availability of the brake system in terms of both the normal brake function and the wheel-specific brake-pressure regulating function is very important in terms of safety.
It is to be expected that, in the future, motor-vehicle brake systems will also be used, which are suitable for motor vehicles for automated driving. These brake systems essentially have to be electronically controllable systems or brake-by-wire systems. This means that a braking command can be made via electronic or electrical control signals by a computer system acting as a virtual driver and implemented by the brake system without any intervention on the part of the driver. For safety reasons, particularly in such combined systems, it is necessary to ensure sufficiently good availability of the normal brake function and also the externally controllable brake function with wheel-specific regulation.
WO 2012/150120 A1 describes a brake system for motor vehicles, which comprises four hydraulically actuable wheel brakes, a pressurizing-medium reservoir under atmospheric pressure and a first electrohydraulic brake control device, which comprises a master brake cylinder, an electrically controllable pressure-providing device, a pressure-regulating valve arrangement for adjusting wheel-specific brake pressures and a wheel-specific output pressure connection for each wheel brake.
The brake system further comprises a second electrohydraulic module having electrically controllable pumps and electrically actuable valves, which is arranged hydraulically upstream of the pressure-regulating valve arrangement of the first brake control device, wherein the suction sides of two pumps of the second electrohydraulic module are connected directly to the pressurizing-medium reservoir. This is disadvantageous in that, in addition to the first brake control device, the second module also has to be connected to the pressurizing-medium reservoir and in that the second module has to be connected to the first module with a further four hydraulic connections, which involves a high level of complexity even when the second module is arranged adjacent to the first brake control device and can result in a plurality of long connecting lines when the second module is arranged at a spacing from the first brake control device.
Moreover, in terms of the hydraulic-connection technology, to integrate the second module into the first braking device, it is necessary to provide additional connections for the second module upstream of the pressure-regulating valve arrangement or upstream of the isolation valves of the first brake control device. This addition of a plurality of hydraulic connections involves complex intervention in the hydraulic component arrangement of the first brake control device in such a way that a corresponding mechanical adaptation thereof is not possible. It is instead necessary to produce a further, structurally different variant which is prepared for connecting the second module.
The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.